Filter cartridges are used for cleaning or purifying gases or liquids. In this context, the fluid loaded with particles to be separated out flows against the wall of the filter cartridge, which is permeable only by the fluid. As the medium, forced by a pressure difference, passes through the wall of the filter cartridge, the particles are separated out and the fluid exits, cleaned, on the other side of the wall.
German Patent No. 44 27 817 A1 describes a filter cartridge which includes a cylindrical filter pad. The pad is made of a layered nonwoven fabric and pleated parallel to its axis. During filter operation, the filter receives flow-through radially toward the interior space, so that the clean-gas (downstream) side is situated in the interior of the cylinder. Manufacturing this filter cartridge takes place such that a strip of filter nonwoven fabric is first pleated and then conveyed into a cylindrical shape, the ends of the strip being bonded to each other. In the area of the two end sides, the resulting tube is glued, dust tight, to a plastic cover or base.
Conical filter cartridges also are used in various filter systems, with glass fiber paper often being used as a filter medium. In this context, the design is similar to that of the cylindrical filter cartridge. Conical shapes are relatively complicated compared to cylindrical shapes, however, and therefore present difficulties in the formation of a conical tube.